Sex differences in lifespan in mammals, from the perspective of sexual selection and reproductive costs.
In the wild world of many mammals, there is a tendency for females to live longer than males, but one of the reasons for this is likely to be due to sexual selection and related behavior . A research report was published last year.
The study was carried out by a joint reserch team from Germany , Denmark, France Hungary and Belgium, and involved comprehensive data analysis and comprehensive data analysis of 528 species of mammals and 648 species of birds kept in zoos.
The paper was published in the scientific journal " Science Advances " as an example of the largest - scale study on the average lifespan of adult sea breams.
The research team also conducted a survey on a population of 110 species that live
The researchers found that in mammals, adult females live about 12 percent longer than males, while in bird species, adult males live 5 percent longer than females.
In addition, the difference in lifespan due to gender tends to be more pronounced in wild animals than in zoo animals, but this is thought to be due to factors such as the harshness of the natural environment and the stress caused by predators.
There are multiple theories as to why these sex differences in lifespan occur, and the main theory is the "heterogametic hypothesis" which suggests that is caused by the sex chromosomes.
In other words, females with two copies of the X-chromosome are said to be more resistant to genetic diseases than males with only one copy.
In contrast to the mutations that occur in the X chromosome, that mutation is likely to maifest itself as a harmful and undesrirable effect, which may ultimately lead to a shortened lifespan.
It is thought that this hypothesis can also be applied to birds, but in the case of birds, males have two Z chromoes. Since females only have one Z chromosomes and one W chromosomes, males tend to live longer than birds in birds.
However , there are many examples that cannot be fully explained by this theory; for example, in some birds of prey, males live longer, which is a general tendency among birds.
Studies have shown that female peregrine falcons and hawks live longer than males at zoos, and reports have also been published.
In addition, the effects of sexual selection and reproductive costs on sex differences in lifespan were also examined.
According to a theory called the "Sexual Selection Hypothesis, when males compete for females, they tend to expand energy in excess by increasing their body size and horns, even at the cost of sacrificing their own survival.
As a result, there is a possibility that adult females live longer than males.
On the other hand, when we analyzed data from zoo animals, we found a trend that was contrary to the " reproductive cost hypothesis".
In other words, females who could shoulder the burden of raising children lived longer than males.
This phenomenon may seem counterintuitive,but if you look at it from an evolutionery perspective, it makes sense.
In other words, due to the nature of child-reraring especially when offspring to survive for alonger period of time , in order for the offspring to be able to reproduce as adults.
Furthermore, the species system in which only the female is responsible for raising children is due to polygamy, in which the male attempts to mate with multiple females, and since the male chooses mating behaviour that consumes a large amount of energy, it works as a disadvantage for survival.
These research results may provide important clues for a deeper understanding of the evolutionary background and ecological strategies of sex differences in lifespan in mammals.
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